Stimulants and depressants both affect your nervous system and brain function, although in opposite ways.

Stimulants excite your nervous system. They may increase your blood pressure and heart rate and give you more energy. In high doses, they can cause insomnia and make you jittery and impulsive (1).

Examples of stimulants include mild ones, such as caffeine, as well as much stronger prescription amphetamines or illicit drugs like cocaine.

On the other hand, depressants slow you down by decreasing your heart rate and blood pressure. They can help you feel relaxed and, on the extreme end, completely sedate you (2).

Benzodiazepines are one class of depressant drugs used to treat insomnia and anxiety, while prescription opiates are powerful products in this category.

Some compounds can have characteristics of both. Examples include nicotine, although it’s most frequently characterized as a stimulant, and alcohol, which is primarily a depressant but has some stimulant effects (3, 4).

You should not mix alcohol and stimulant or depressant drugs due to the risk of severe side effects.

Summary

Stimulants excite your nervous system and may boost your energy, while depressants slow down your nervous system and relax you. Some substances have both stimulant and depressant effects.

Initial doses of alcohol signal your brain to release dopamine, the so-called “happy hormone,” which can cause you to feel stimulated and energized (3).

In addition, alcohol can increase your heart rate and may lead to increased aggression in some individuals, both of which are typical of stimulants.

Stimulant effects occur when your blood alcohol concentration (BAC) approaches 0.05 mg/l but are replaced by more depressant effects once your BAC reaches 0.08 mg/l — the level at which you’re considered legally impaired to drive in most areas of the United States (3).

One important thing to note is that the effects of alcohol vary greatly by individual and are influenced by a number of factors, including your body chemistry, sex, weight, alcohol tolerance, and the dose of alcohol consumed.

To get a rough understanding of how many drinks it would take you to reach these BAC levels, there are many calculators available online.

Furthermore, some people may experience more stimulating effects from alcohol, while others may experience more depressant effects. Researchers theorize that people who experience more stimulating effects and fewer sedative effects are at a higher risk for alcoholism (4).

However, while it has some stimulant effects — particularly in low doses — alcohol is mainly a depressant substance.

Summary

Alcohol has an initial stimulant effect in lower doses. It can increase your heart rate, aggression, and impulsiveness, as well as cause a surge in dopamine levels.

In turn, people who have ingested large amounts of alcohol have slower reaction times and may seem sleepy, disoriented, or sedated.

In addition, higher doses of alcohol can suppress dopamine production, which can make you feel sad or listless (3).

Depressant effects of alcohol occur when your BAC reaches about 0.08 mg/l. Once your BAC reaches 0.2 mg/l or greater, its depressant effects on your respiratory system can become so powerful that they cause coma or death (3).

Summary

In larger quantities, alcohol switches from a stimulant to a depressant. It slows down your nervous system, blood pressure, and heart rate, leading to mental fogginess, drowsiness, and lack of coordination.